There has been conventionally disclosed a storage assembly which is loaded in a storage tank and in which a cylindrical rib is protruded on each of a lower surface and an upper surface of each partition plate, funnel-shaped end spacers each of which has a large-diameter portion which is connected to the upper and lower surfaces of the partition plate while being fitted to the cylindrical ribs and a small-diameter portion having a diameter smaller than that of the large-diameter portion, and both ends of a cylindrical coupling spacer are fitted to small-diameter portions of a pair of end spacers (see, e.g., Patent Literature 1). In this storage assembly, assuming that a length of one side of the partition plate is S, a diameter of a portion where the cylindrical rib is fitted to the large-diameter portion is set to fall within the range of 0.40 S to 0.95 S. Further, horizontal coupled bodies, each of which is constituted by aligning a plurality of partition plates on the same horizontal plane and coupling them, are provided on a plurality of steps, and the end spacers and the coupling spacers are interposed between the horizontal coupled bodies on the plurality of steps. Furthermore, styrene foam plates are arranged to abut on outermost surfaces of the plurality of end spacers placed on the outermost sides in the plurality of end spacers of the storage assembly loaded in the storage tank, the styrene foam plates are configured to surround the end spacers and the coupling spacers in accordance with each space between the horizontal coupled bodies on the plurality of steps.
In the thus configured storage assembly, the partition plates, the end spacers, and the coupling spacers receive a partial pressure in a vertical direction in external force which acts on the storage assembly, and the horizontal coupled bodies mainly receive a partial pressure in a horizontal direction in the external force which acts on the storage assembly. Consequently, even the storage assembly formed by assembling members having relatively simple shapes can assure strength as a relatively large structure. Moreover, in the storage tank loaded with the storage assembly, when the storage assembly and the styrene foam plate are wrapped with an impervious sheet, even if the partial pressure in the horizontal direction in the external pressure acting on the storage assembly acts in a direction to be pressure-welded to the impervious sheet, large-area planes of the styrene foam plates receive this external pressure. Consequently, damage to the impervious sheet can be avoided.